2E3: Radiation and the Thermal Environment

1. 2E3: Radiation and the Thermal Environment Ionising Radiation

2. Ionising Radiation Particulate: Alpha Radiation Beta Radiation Non-Particulate: Gamma Rays X-Rays Neutrons

3. Alpha Radiation Very short range Stopped by air, paper or skin Not a hazard outside the body A concern when inside the body – cause intense local ionisation and biological damage

4. Beta Radiation Longer range than Alpha Low energy beta radiation does not penetrate the skin, but high energy beta can penetrate soft tissue to a depth of over one cm. Beta inside the body is a concern, but less intense than alpha

5. Gamma & X-Rays Both electromagnetic radiation Gamma radiation is emitted continuously by radioactive decay X-rays are generated in special electrical equipment by bombarding a target with electrons Consequently, an x-ray beam only exists when machine is on, whereas gamma rays are emitted continuously Penetrating power of electromagnetic radiation depends on its energy and the properties of the matter through which it passes X-rays are able to pass through the human body, but gamma and x-rays can be stopped by lead shielding

6. Neutrons Emitted during certain nuclear processes such as nuclear fission Great penetrating power Produce ionisation directly and can cause great harm as they pass through the body

7. Workplace Examples of Ionising Radiation Industrial Radiography (e.g. for NDT) Medical, dental and veterinary x-ray equipment Nuclear power generation

8. Measurement Ionising radiation is measured in sieverts (Sv) Sv include a weighting factor to take into account differing biological effects of alpha, beta, gamma and neutron radiation Exposure is controlled by dose limitation, which is based on the premise that for conditions having no safe threshold, exposure is reduced to a level where probability of harm is small

9. Ionising Radiation Health Effects Nausea and vomiting Reduction in bodies defences Reddening of skin Loss of weight & hair Blistering and ulceration of skin Cataracts Cancer Genetic defects (affects subsequent generations)

10. Dose/Response Relationship Some effects of ionising radiation are dose dependent and only occur if dose received is above certain level: Radiation sickness, skin burns or cataracts Other effects are not dose dependent. Any exposure to radiation may cause the effect. However, likelihood of harm increases at higher levels of exposure: Cancer, Genetic defects

11. Detection Film badges (personal) Ionisation chamber Geiger counter Personal air samplers Analysis of faecal and urine samples

12. Control Measures Based on 3 principles: Shielding Distance Reduced time exposure Shielding is best method as it reduces risk positively. Distance and reduced time exposure are administrative controls which require considerable supervisory control

13. Engineering Controls Shielding Containment Ventilation Glove boxes or fume hoods Under negative pressure

14. Procedural Controls Restricted access IRR99 require designation of: Controlled areas (dose is likely to exceed three tenths of dose limit) Classified persons (personal exposure likely to exceed three tenths of dose limit) Supervised areas (dose likely to exceed one tenth of dose limit) Systems of work Permit to work reduces time exposure

15. Procedural Controls PPE Gloves, overalls, eye protection, RPE etc. Local Rules: Hazard assessment Contingency plans Radiation protection advisor Monitoring procedures etc. etc.

16. Ionising Radiation Regs 1999 Employer must ensure that employees (18 and above), trainees (less than 18), women of reproductive capacity and other persons are not exposed to ionising radiation to an extent that exceeds annual dose limits in Schedule to Regulations Requirement to restrict exposure sfairp includes: Proper maintenance, examination and test of engineering controls, design features, safety features or warning devices Provision concerning pregnant or breast feeding women

17. Classified Workers Definition: Someone likely to receive radiation dose of more than 3/10ths of any relevant dose limit Someone likely to receive effective dose of more than 6mSv per year Must be over 18 years old Certified as fit for the work by appointed doctor or Employment Medical Advisor Someone who may enter a “controlled” area

18. Classified Workers Specific Arrangements: Dosimeters/film badges to measure exposure Assessment of significant doses Use of approved dosimetry service Provide health surveillance Keep records of doses/health checks etc.

19. Previous Exam Questions In relation to the Ionising Radiation Regulations 1999: i.) Explain what is meant by the term “classified worker” ii.) Outline the specific arrangements that must be made by employers for employees who are designated as “classified workers” (10 marks)